Self-igniting incendiary devices



w. o. SNELLING 2,958,277

SELF-IGNITING INCENDIARY DEVICES Filed May 9 1941 VIQZZer a fizzellz'qg.

2,958,277 SELF-IGNITHNG INCENDIARY DEVICES Walter 0. Snelling,Allentown, Pa., assignor to Trojan Powder Company, Allentown, Pa.

Filed May 9, 1941, Ser. No. 392,781

7 Claims. (Cl. 102-6) This invention relates to self-igniting incendiarydevices and has for its primary object the provision of such a devicewhich can be transported with reasonable safety as when carried in anairplane and which will delay action when dropped in surroundings whichare temporarily unsuitable, as for example where the terrain is too dampor too cold or both, and which during such a delay is protected againstinactivation.

A further object of the invention is to provide an incendiary devicecontaining a self-igniting material. and a chemical heating compositionwhich insures positive action when conditions are favorable forignition.

A still further object of the present invention is to provide anenvelope for any sort of incendiary device which will preserve thecontents in active condition as long as the device is in damp or coolsurroundings.

During the present war use has been made of incendiary devices doubtlessincluding phosphorus which spontaneously takes fire as soon as thesolute, usually carbon bisulfide, evaporates. An example of suchincendiary devices is the so-called leaves which have been dropped onGerman forests and are utterly wasted if dropped during a rain or whenreasonably heavy dew is on the foliage for under such circumstances thepreviously known incendiary devices will ignite quite independently ofthe wetness of the surrounding inflammable objects.

It the incendiary devices are water-wetted before dropping, it isrecognized that these previously known devices will not be instantlyacting. But the delay caused by simple surface wetting is not sufficientto prevent partial oxidation or slow smouldering over a long period ofexposure. This premature action inactivates the device for subsequentproper functioning when the surroundings become favorable for ignition.I have found that surfaces coated with phosphorus from a carbondisulfide solution may not function at all if the coated surface iswaterwetted before exposure, particularly if dropped in a cool or windyplace. Slow oxidation does start and makes it self evident by the wispsof fumes given off, but in a cool or windy place the heat is dissipatedas rapidly as it is liberated; and the temperature of the phosphoruscoating will not rise high enough to actuate ignition.

Larger pieces of phosphorus likewise become inert or ineflicient wheninitially exposed to a cool or damp atmosphere. With the larger pieces,a new cause of the failure becomes evident. The oxidation, slowed downby unfavorable surrounding conditions, produces a deliquescent coatingof phosphoric oxide and perhaps other which avidly combine with moistureto form a persistent, continually wet film of phosphoric acid. Onsubsequent exposure to sunlight, the rate of oxidation is furtherretarded in spite of the increased warmth, due partly to a coating ofred phosphorus which results from the actinic exposure. Once theseretarding coatings have formed, it is unlikely that the phosphorus willever ignite unless the temperature of the surroundings rises to at least34 centigrade or 90 Farenheit, the ignition temperature of phosphorus.In cool surroundings, a coated phosphorus does 2,958,277 Patented Nov.1, 1960 not experience a sutficient temperature rise through its ownoxidation to approach this ignition point.

My invention provides for a device which does not allow theself-igniting charge to begin to function until the surroundings aresuitably dry, regardless of how many intervals of partial drying-out maybe experienced. In one form of my invention a chemical heating compoundprovides for a sudden liberation of heat when the surroundings becomedry, this heat raising the newly exposed phosphorus well above itsignition point and causing the de vice to function with positive action.

Since the ordinary incendiary device is incapable of both drying thematerial and igniting it, only relatively poor functioning of previousdevices is possible under unfavorable conditions. It is a prime objectof the invention to delay the action of the self-igniting incendiarydevice until such time as the surrounding objects may have dried out andtherefore become inflammable when subjected to the flame of the presentdevice.

In the general form of my invention, the body or container incorporatesthree separate functions: (1) to protect the self-igniting material fromthe atmosphere until the surroundings are suitably dry; (2) todisintegrate in part or entirety, as by shrinking or cracking after thesurroundings have become dry, thus exposing the fresh selfigniting coreto the atmosphere and causing it to function; and (3) to furnishadditional combustible material for the incendiary device after theself-igniting material has functioned, thus intensifying its heat andflame.

This container body should have suflicient initial strength to withstandthe impact from dropping a great distance, since these devices would beused principally by the flying service, and it should be sufficientlywater-resistant initially to resist moisture penetration during longtime storage under Water or in humidors. It may be pigmented, or paintedor otherwise given a suitable drab color to minimize detection before itfunctions.

The shape and size of the body or container may vary widely, dependingupon the ease of manufacture and assembly, as for example whether apelleting machine or extrusion machine is used. If desired, the shapemay be such as to increase air resistance and minimize the impact whendropped from a great height. The walls may be quite heavy, and serve asfuel; or quite thin and of comparatively negligible weight. The lattertype makes a unit weighting considerably less than an ounce. These maybe distributed in great quantities as an incendiary match for verycombustible surroundings, or such lightweight units may be tightlyfitted into perforated powder pellets which then furnish a more intenseflame when they function. This particular arrangement has the sameadvantage as obtained in the well known practice of separatingquantities of detonators from quantities of dynamite sticks orexplosives cartridges through long storage, and not combining them untilthey are used.

In the drawings:

Figure 1 is a vertical section through a preferred form of my invention.

Figure 2 is an end view.

Figures 3 to 7 are sections through variant forms of my invention.

Figure 8 is an end view of the device of Figure 7.

Fig. 9 is a central cross-section through the device of Figure 4.

Fig. 10 is a simple and eflicient form of the invention.

The preferred form of self-ignited incendiary device is shown as thecentral element of Figure 1. This form is so simple and economical inconstruction, and can be made in such small sizes, that great numbers ofthem can be packed in a relatively small space, in suitably sealed humidcans which permit safe, easy transportation and distribution. In thistype the non-breakable, preferably inflammable outer cover or container31 has its open end or ends sealed by a layer of firm water-swelledsubstance 32 such as can be made from starch-paste, gelatin or gluegels, agar-agar, pectin, silica-gel, alumina-gel, bentonite or clay,viscose, or the like, or combinations of these; In the case of thestarch-paste, which type is preferred, the'sealing material may'bep'o'ufed'in'as a'cold fluid before the gel has set. The resultingplug serves as afirm, air-tight seal as long as the device remains inhumid or vv'etsurroundings, but shrinks and exposes the contents in adry and favorable atmosphere.

Because of its confinement, and the depth of the layer, this plugordinarily will not dry out beforetlie surroundings do, but to insurethat the seal remains intact until the surroundings are quite dry, Iprefer to add avery small quantity of a hydroscopic agent such asglycerol, sorbitol, ammonium nitrate, calcium chloride, or the like, orsuitable mixtures of thesewith the gel material, the amounts dependingupon thewater content and thedsired rate of drying. The'resultingwaterswelled plug insures that the surroundings are thoroughly drybefore the self-igniting composition is exposed to the air which causesit to function.

The self-igniting composition 33 immediately inside the container andprotected from exposure by the waterswelled plug, may consist of anymaterial which is stable when kept wet by air-free water or othersuitably inert volatile fluid, but which oxidizes'so rapidily onexposure to the atmosphere that it gives off a continually increasingamount of heat until ultimately it either bursts into flame itself orignites the inflammable surrounding matter. Such self-ignitingcompositions may consist of a simple phosphorus pellet; or a looseabsorbent having the desired wick effect, such as pulp, paper, cotton ornitrocotton, or starch nitrate powder, partly saturated with a solutionof white phosphorus in carbon disulfide, or in benzene, ether, or othersuitable phosphorus solvent; or it may consist of suitable inertabsorbent'or inflammable absorbent contain ing spontaneously inflammableoil or oils such as triethyl phosphine, bismuth ethylchloride, cacodyloxide, boron triethyl or the like; or it may consist of a highlyinflammable composition mixed with a water-wet or alcohol-wet pyrophoricmetal, such as amorphous zirconium, or black amorphous catalyst nickel,cobalt, iron, or the like, or pyrophoric lead, keeping such pyrohoricsubstances protected from exposure by a coating of air-free water orother volatile inertfluid, which in turn is confined by thewater-swelled plug 32.

When the water-swelled plug dries out, the volatile phosphorus solventevaporates through the exposure, and the wick action of the absorbentduring this evaporation produces a tendency for the phosphorus toaccumulate on the evaporating surface, where its oxidation isintensified and ignition'insured. As long as the water-swelled plug 32is kept from drying out and shrinking, either by close confinement or byhumidification in the storage containers, the seal remains intact andthe carbon disulfide cannot evaporate, so the self-igniting layer cannotfunction, nor can it deteriorate. When it falls to a place havingsuitably dry conditions, the water in the starch-paste or similar gelevaporates, causing the plug to shrink and break away from the wall ofthe container. The carbon disulfide evaporates through 'thisopening,causing white phosphorus to accumulate nearby. In this fresh and finelydivided condition the phosphorus starts to oxidize as soon as the heavysolvent fumes escape and allow the entrance of air; the heat ofoxidation soon raises the phosphorus to the kindling point and this inturn ignites the inflammable case and the veryinflammable'absorbent'next to the main body of combustible material.

The main body of combustible'material 34 is preferably made of a mixtureof starch nitrate and an'oxidizing agent, but could suitably be made ofany highly inflame mable combination of combustible and oxidizing agent,respectively, such as sugar and potassium chlorate; or

charcoal, sulfur, and sodium nitrate; or aluminum and barium nitrate.The main body of material 34- may be separated from the self-ignitinglayer 33 by a pyroxylin washer 35, or film of col'lodion, or both, toprevent diffusion of the phosphorus solvent or pyrophoric wetting agent,or other action during a long period of storage. Using the preferredmixture of starch nitrate and oxidizing agent, I have found itconvenient after pressing this into the container to apply a few dropsof acetone or other volatile starch nitrate solvent, which readilyevaporates and leaves a hardened surface suflicient for this purpose. Asmall quantity of startch nitrate is placed on top of this, and then afew drops of solution containing about l050%, preferably around 30%,white phosphorus in carbon disulfide. This is quickly covered over witha layer of suitable starch-paste or similar hydrophile which on standingsets to a firm gel. These units are then stored by close confinement ina humid container, preferably filled under slight pressure by an inertgas such as carbon arenas or 'nitro gen.

I havemad'e'units of this 'type so small that they weigh considerablyless than an ounce, and many thousands of them" some beca'rried'in anaverageaircraft load. While the size and duration of flame resultingfrom one of these units is more than enough to ignite readilycombustible matter, the intensity can be greatly increased by the use ofperforated powder pellets36' of any size or shape desired, into' whichthese small units would be tightly inserted just before distribution.The perforated pellet 36 could'suitably be made of the same combinationof a combustible and oxidizing agent as described for the main body 34,or even a less sensitive incendiary charge, for example, it mayadvantageously be made of a thermite composition such as aluminum andiron oxide, as the smallunits having the main body filled with mypreferred mixture will readily ignite thermite.

Figure 3'shows another form of my invention, in which the inflammablebody 37 is made so thick that it serves the same purpose as the pellet36 shown in Figure l, intensifying the heat and flame of the combustion.The water-swelled plug 38 and the self-igniting mixture 39 may be thesame as before, and in this case no outside shell is needed as aseparate container and no main body of filler is required as the heavycontainer body 37 itself furnishes the main quantity of incendiarymaterial. The conventional pattern illustrated with a single opening canreadily be formed by pelleting but when formed by extrusion the bodywould have the central cavity completely thru as in Figure 4, thusrequiring two plugs 38. This insures proper functioning in case thedevice lands with one opening imbedded against the ground. In eitherform, as in the device of Figures 1 and 2, the container body 37 is madeof an unbreakable, very inflammable plastic such as is made fromnitrated cotton or nitrated starch or similar material properlyplasticized.

In another form of my invention, shown in Figure 4, there is nowater-swelled plug as the container 41 itself is so made that itdisintegrates by cracking or shrinking or warping on drying out, thusexposing the self-igniting mixture. This container 41 is made fromunplasticized non-breakable inflammable plastic material mixed with avolatile solvent or solvent-blend which evaporates in suitably drysurroundings and causes the protective container to break open, mainlyby cracking. If desired, specific lines of weakness, 45, may be moldedor cut in, to'insure that the container breaks in the manner desired, ondrying out, but a properly made composition will crack as desiredwithout such weakness. A suitable composition may be very low viscositynitrocellulose, or preferably starch nitrate, without any plasticizerbut colloided with a volatile solvent such as butyl acetate. Amylacetate and butyl propionate are also suitable solvents, although theyevaporate more slowly and thus cause slower cracking of the container.Ethyl acetate is faster in its functioning but is too water-soluble forlong underwater storage. For this reason I prefer butyl acetate, andmake a colloid with starch nitrate containing from about 15% to 25% ofthis solvent, which gives the mixture a consistency resembling that ofstiff pie dough. However, the solvent ratio and therefore theconsistency of the colloid may be widely varied, depending upon whetherit is extruded or pelleted, for example. While true plasticizers must beavoided, small quantities of waterproofing agents such as butyl stearateor paraifin oil or the like may be added. These swea to the surface andimprove the water resistance for long periods of storage under water.

Since no water-swelled plug is required for this type, the ends may betightly sealed by a waterproof film 42 such as collodion ornitrocellulose or ethyl cellulose, and the contents inside kept quiteprotected from water even though the unit may be totally immersed inwater for storage. Under these circumstances, and the somewhat slowerrate of exposure due to the shrinking of the case 41, I have found itsuitable to use more active self-igniting mixtures 43 which aredecomposed by water and therefore cannot be used successfully inproximity with a waterswelled plug. Thus other spontaneously inflammablemetal-alkyls such as zinc dimethyl or zinc diethyl may be used here,besides the water-stable types such as boron triethyl and the pyrophoricmetals previously mentioned. I have also found it desirable, when usingthis water-tight closure 42, to augment the action of the self-ignitingcore by employing a chemical heating compound which does not react untilit is exposed to air or moisture. For example, an acid anhydride such asphosphoric anhydride or arsenic anhydride or selenic anhydride may beintimately mixed under an inert solvent such as petroleum ether orbenzene with a dry base such as calcium hydroxide or magnesium hydroxideor the like. I prefer to use a mixture of phosphoric anhydride andcalcium hydroxide, mixed to a pasty solid with pertoleum ether. Thephosphoric anhydride must not be in excess, but should be inapproximately molecular proportions with the base, or less; otherwisewhen it starts to react it may form a surface syrup or a glaze, eitherof which will prevent proper functioning. Small pieces of phosphorus 44may be directly incorporated into this pasty solid 43. Such a mixture iscatalysed to reaction by a small amount of absorbed water-vapor, and theintense heat of reaction is more than enough to raise the exposedphosphorous to its kindling point, thus igniting the incendiary device.Nevertheless I have found this mixture to be quite inert as long as itis protected from moisture by the petroleum ether and the confinement ofthe colloided case 41. The small pellets of phosphorus 44 may varyconsiderably in size, but must be quite free from water; they may bedistributed through the heating compound, as shown in Figure 4, whichillustrates an extruded container, or the phosphorus may be concentratedin one lump at the inner end if a pelleted or molded container such asshown in Figure 3 is used.

Figure 5 illustrates the same type of incendiary device functioningthrough disintegration of the container, but

in this form the moisture-sensitive contents 47 are protected by athicker piece 48 at one or both the end closures, depending on whether"or not the central well extends entirely through the body or onlypart-way. This end closure is made of the same colloided material as themain body 46, and may be cemented to it either with a suitable solventor with a collodion mixture or similar cement 49.

While I much prefer a plug to a film, the latter has definitepossibilities either with or without an enveloping glass case. In theform illustrated in Figure 6 the body 50 has a central well 51 extendingpartly or all the way through the body to house the potentiallyspontaneous igniting agent as before, for example, an absorbent materialsaturated with phosphorus. In this modification the body and itscontents is completely inclosed in an envelope or cover 52, preferablyof thin sheet material which shrinks upon drying and therefore willbecome ruptured when fully dry, thus admitting air to the self-ignitingagent or mixture held by the absorbent material in the well 51.

The pellet 50 is preferably made of a mixture of starch nitrate with anoxidizing agent but could almost as well be made of any highlyinflammable mixture such as po tassium chlorate and sugar; or a mixtureof sodium nitrate, sulfur and charcoal; or a mixture of barium nitrateand aluminum powder or flakes, or other mixture of a combustible agentwith an oxygen-carrying salt. As stated, I prefer a mixture of starchnitrate with an oxidizing agent and press this mixture into the annulardisk of the shape shown.

The protective covering 52 having the delay action might be a merecoating of any lacquer or paint that would crack or disintegrate upondrying, a mixture of glue and water, or a material such as agar-agar inwater and if desired, loaded with finely divided clay or bentonite. Areasonably thin viscose cellulose sheet shrinks to a great extent upondrying and by being made both thin and weak it ruptures when shrunk byexposure to dryness. The film or envelope could be of a substance thatwill disintegrate by loss of volatile solvent. The best material triedso far is starch nitrate. The time of rupture of the envelope can becontrolled to a chosen degree of dryness depending upon conditons uponwhich it is used, as for example, by incorporating into the envelope ahygroscopic substance ;or a combination of such substances. As onetypical example, I mix ammonium nitrate with the viscose solution beforemaking it into sheets and when this material forms the coating thedrying of the envelope will be delayed until after the air has dried outthe ammonium nitrate solution, thus preventing premature action of theself-igniting agent and delaying the flame projection until the degreeof dryness in the surrounding atmosphere is more favorable to theeffectiveness of the incendiary device.

Inasmuch as these self-igniting incendiary devices are to be usedprincipally in the flying service it is essential that they should beinsured against premature action, not only in transit but after thedevice has been dropped from the airplane and has landed on the ground.If these devices fall in a damp place the humidity will prevent anyshrinking of the outer envelope and nothing will happen for a time. If,however, the dampness in the vicinity of the device is only temporary,the envelope 52 will dry after the surrounding material has dried andwith the cracking of the envelope the dry air will enter and will ignitethe phosphorus which in turn will kindle the pyrotechnic compositionforming the body 50 and this, by throwing a great flame, will ignite thenowdry inflammable material in the vicinity.

Figures 7 and 8 show an incendiary device which is a combination of twodiiferent waterproof, inflammable solv-ated plastics forming the twohalves 59 and 60 of the container body. Both halves initially containapproximately equal quantities of volatile solvent, but one half driesto a considerably stronger material than the other. Thus as the solventevaporates from both surfaces of the two different halves of plastic,the contracting force on the surface of the stronger plastic 59 causesit to buckle or break away from the weaker half 60, thus causing theweaker half (or the joint) to break and expose the inclosedself-igniting composition 62. The two halves may be cemented togetherwith a mutual solvent or with collodion or suitable material 61 afterplacing in either half a quantity of the self-igniting composition,preferably the pasty solid containing small pellets or chips ofphosphorus 44 and a heating mixture consisting of phosphoric anhydrideand calcium or magnesium hydroxide, mixed in petroleum ether.

While in Figures 7 and 8 the device is shown with its axial dimensionsless than the diameter, the body of this cylindrical incendiary may beelongated as in Figure 4 inwhich case each; ofnthe two halves will beshaped like thetcontainersi of Figures 3 and 5 withv their open-endsfacing each iother thus employing no plug as both ends are solid for thecentral well is partly in each-half asin Figure 7, orequally obviouslythe hollow cylindrical bodyAl-mffigure 4 maybe intwo longitudinal halvesasin the case :of'the. commonlead pencil, save that the two halvesareo-f-unequal strength.

Inasmuch .as of. these self-igniting incendiary-idevices are tobeusedprincipally in' 'the flying service it is essential that =theyshouldbe insured against premature action, not only when the device has landedin damp or cold surroundings, butalso before and-during transit. Thesmall compact incendiary devices described as the central element ofFigure 1 readilyqadapt themselves to close-packing, in humid containers,preferably air-tight containers inwhich the air. is displaced by aninert gas such as carbondioxide or nitrogenunder slight pressure, suchcontainers would be made to open immediately be-- fore discharging thedevices from the plane, or immediately after dropping from the plane bya delay-action spring device or pressure generator or any 'similardevicewhich breaks ?the container with sufficient force to scatter the unitswithout damagi-ng'them. Any of my incendiary devices may be packed inthismanner.

However, as in Figure 6 each incendiary unit may be separately enclosedin a frangible envelope or complete cover 55 such as'thin glass, whichis shattered by the impact when the'device hits the ground. As long asthis frangible envelope remains intact, as in transit or long storage,the film 52, the water-swelled plug 32 or 38, or the solvent-wetcontainer which disintegrates on drying, remain unchanged and keep theself-igniting composition eifectively-sealed. The efficiency of eithertype is increased by'the autogenous sealing of the device in thefrangible container filled with carbon dioxide, nitrogen, orotheninert-gas, preferably under slight pressure with respect to that ofthe atmosphere.

What I claimis:

1. An incendiary device comprising a self-igniting agent of the typewhich rapidly increases in temperature tothe kindling point-when exposedto the air, an enclosing casing initiallyprotecting the agent from theatmosphere but composed at least in part of a material slowly deformablewhen exposed to warm -dry air to admit air to the agent toinitiateignitiomin which the casing is a water-proof container having a deepcentral well, and a water swelled plug closing said well.

2. An incendiary device comprising a self-igniting agent of the typewhich rapidly increases in temperature to the kindling point when XPOSedto the air, an enclosing casing initially protecting the agent fromtheatrnosphere but composed at least in part of a material slowlydeformable when exposed to warm dry air to admit air to the agent toinitiate ignition, in which the casing is a hollow container in whichthe agent is;,sealed at one end with a plug which shrinks to form crackswhen dried.

3. Th me h t=mak n s ti it e in e dia y device which consistsdn formingacontainer with a central cayity,;partly filling the cavity with amixture of a com-bustibleand an oxidizing-agent, applying to the packedmixture a solvent ;for the combustible agent to form a hardened surface,then packing in the cavity an absorbent, saturating the absorbent-with asolution of white phosphorus in carbonbisulfid and then sealing thepacked cavity with a hydrophile paste which sets on standing to a firmgel.

4. An incendiary device comprising a pellet of inflammable -material'having therein a central well whose diameter is a small fpaction of thediameter of the pellet, a test-tube shaped inflammable container fittingsaid-well, a selfigniting agent in the container, and a plug closure .ofwater-swelled material to preventaccess of air to the agent, saidclosure shrinking-in a dry atmosphere to expose the agent forrapidkindling.

5. Thedevice of claim 4 in which a body of combustible material; fillsthemajor portion of the container, the agent-isbetween said body and theplug, and {the pellet is of less sensitive incendiary material than thebody'ofpornbustible material in the container.

6.'T.he device of claim 5 in which the pellet is of a thermitecomposition.

7. Thedevice of claim 2 in which the casing is an elongated tube closedat the endopposite the plug.

References Cited in the file of this patent UNITED STATES PATENTS2,558,726 Barker July 3, 1951 FOREIGN PATENTS 24,275 Great Britain 1914

4. AN INCENDIARY DEVICE COMPRISING A PELLET OF INFLAMMABLE MATERIALHAVING THEREIN A CENTRAL WELL WHOSE DIAMETER IS A SMALL FRACTION OF THEDIAMETER OF THE PELLET, A TEST-TUBE SHAPED INFLAMMABLE CONTAINER FITTINGSAID WELL, A SELF-IGNITING AGENT IN THE CONTAINER, AND A